clays and binders

Monmorillonite and charcoal

This was a pretty simple experiment, what percent at a given concentration can be removed by coconut shell MAC vs APM. It is not clear what the pH was in this pre screen the concentration of the binders, or other anions or cations in the solution. The time for binding was also not given.

Adsorption percentage at different concentrations of As (III, V) (A), Cd (II) (B), Hg (II) (C), and Pb (II) (D) onto 1 mg/mL APM and MAC Data represent the mean percent adsorption at each concentration, run in triplicate (* p ≤ 0.05; ** p ≤ 0.01)

Methyl mercury was used instead of a halide salt. Nitrate was the counter ion for cadmium and lead. Arsenic is an anion for which sodium was the the cation.

Metal solutions were prepared from pure crystals in pH 2 distilled water. The binders were 1 mg/mL. All samples were vibrated at 37°C and 1000 rpm. The binders were separated from unbound metals by centrifugation at 2000 g for 20 min and analyzed by ICP-OES for As, Cd and Pb, and AAS for Hg.

The APM seems to be binding As and Cd well but with a lower affinity than the MAC. We can hypothesize that there are more low affinity sites in APM vs MAC. APM seems to have higher affinity for Pb than MAC.

In the absorption experiments the bound was inferred by how much was put in the system and what was free in solution. In this set of experiments the binders were transferred to “pH 7 water” In an ideal world the pH would have been adjusted from pH 2 to pH 7 with sodium bicarbonate just as in our duodenum.

Desorption isotherms of As (III, V) (A), Cd (II) (B), Hg (II) (C) onto MAC, and Pb (II) (D) onto APM surfaces, plotted by the Langmuir model Data represent the mean adsorption (g/kg) at each concentration, run in triplicate

Table 3 of this publication says it all. We can assume for now that r2 says that what comes off is proportional to what adhered in the first place.

qmax (g/kg)Kdr2Desorption%
qmax, binding capacity of sorbent following desorption; Kd, binding affinity; r2, correlation coefficient
  • in terms of g/kg, MAC is an okay absorbant for Hg but much less so for Cd and As.
  • The affinity of individual sites is 10x greater for Cd than for Hg and As. The smaller the dissociation the greater the affinity. Confusing.
  • The MAC desorption for Hg is pretty high in unbuffered water. This is generally considered a “no no” in the realms of biochemistry. In this case the binders have the potential to change the pH.
  • The APM seems to have a comparatively high binding capacity for Pb.
  1. Wang M, Rivenbark K, Gong J, Wright FA, Phillips TD. Application of Edible Montmorillonite Clays for the Adsorption and Detoxification of Microcystin. ACS Appl Bio Mater. 2021 Sep 20;4(9):7254-7265. PMC free article
  2. Wang M, Phillips TD (2019) Potential applications of clay-based therapy for the reduction of pesticide exposures in humans and animals. Appl Sci 9(24):5325 10.3390/app9245325 [PMC free article]
  3. Heydarian F, Moshiri M, Roohbakhsh A, Akaberi M, Haghighizadeh A, Ghadiri A, Yeganeh Khorasani N, Etemad L. Effects of multiple doses of montmorillonite, alone and in combination with activated charcoal, on the toxicokinetics of a single dose of digoxin in rats. Iran J Basic Med Sci. 2023;26(8):906-911. free paper
  4. Wang M, Bera G, Mitra K, Wade TL, Knap AH, Phillips TD. Tight sorption of arsenic, cadmium, mercury, and lead by edible activated carbon and acid-processed montmorillonite clay. Environ Sci Pollut Res Int. 2021 Feb;28(6):6758-6770 PMC free article

Barb, I saw the email response from Bob Carpenter at who works with Tim Phillips and Wang at Veterinary Integrative Biosciences at Texas A&M.
I attached TxESI paper that compares activated charcoal with activated calcium montmorillonite clay, arguing that their montmorillonite clay is better than charcoal (see page 11) in that it has pores just like charcoal (macro, meso, micro) plus has both negative & positive charges.
That being said, 2021 Wang, Phillips, Tight sorption As Cd Hg Pb by activ carbon (MAC) and montmorillonite acid-processed (APM) clay shows that MAC is better. It binds Hg whereas APM does not, and it binds As & Cd slightly better than APM, while APM binds Pb. The mixture Fig 4, is not better than MAC alone which the article does not comment on but to me this suggests that MAC is blocking the additional benefit that APM should have since it binds Pb. Alternating MAC and APM may be best, rather than mixing them. Only other thing I noticed is that MAC seems to work better than APM at a lower concentration whereas APM has a linear curve.
On page 10 they state that APM is better (for heavy metals) than Ca or Na montmorillonite or amended with thiamine, carnitine, choline, etc
I wonder why Wang & Phillips are not looking at Zeolite – could it be because Bob Carpenter is not selling this?

Barb, further thoughts. I am fairly sure at this time that binders should not be combined.
I would like to see the 2021 study expand to include alternating MAC and APM.
I would like to see their “data not shown” on CM & SM in which they state that MAC and APM were better than CM, SM, and amended montmorillonite.
Wondering why they talk about other binders yet continually ignore any mention of zeolite clinoptilolite?
Do you think you should contact Tim Phillips regarding these things?

Also, I don’t think any GI binders can be combined besides maybe zeolite (clinoptilolite) and bentonite (montmorillonite). When they discuss charge in that attachment I sent last night, it made me realize that chitosan being positively charged will bind to negatively charged clay which probably would cause clumping and decreased efficacy of both.

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